• 제목/요약/키워드: Relaxor

검색결과 109건 처리시간 0.022초

$0.6Pb(Ni_{1/3}Nb_{2/3})O_3-0.31PbTiO_3-0.09PbZrO_3$ 완화형 강유전체의 전계 유기 상전이 현상 (Field Induced Phase Transition in $0.6Pb(Ni_{1/3}Nb_{2/3})O_3-0.31PbTiO_3-0.09PbZrO_3$ Relaxor Ferroelectrics)

  • 윤만순;장현명;정회승;최병철
    • 한국세라믹학회지
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    • 제34권6호
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    • pp.620-628
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    • 1997
  • The possibility of the existence of a field-induced micro-macrodomain switching was proposed and examined using 9 mol % PbZrO3-doped 0.6Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) systems having rhombohedral symmetry at room temperature. the thermally depoled (freshly prepard) specimens prepared from the rhombohedral side of the system exhibited a relaxor behavior for the whole range of temperature examined (for T

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Growth of lead-based functional crystals by the vertical bridgman method

  • Xu Jiayue
    • 한국결정성장학회지
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    • 제16권1호
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    • pp.1-7
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    • 2006
  • Some lead-based crystals show excellent ferroelectric, piezoelectric or scintillation properties and have attracted much attention in recent years. However, the erosion of the high temperature solution on platinum crucible and the evaporation of PbO component are the main problems often encountered during the crystal growth. In this paper, we reported recent progress on the Bridgman growth of lead-based functional crystals, such as novel relaxor ferroelectric crystals (PZNT and PMNT), scintillation crystals $(PbWO_4,\;PbF_2\;and\;PbClF)$ and piezoelectric crystals $(Pb_5Ge_3O_{11}\;and\;Pb_2KNb_5O_{15}),$ in Shanghai Institute of Ceramics, Chinese Academy of Sciences. The vertical Bridgman method has been modified to grow PZNT crystals from high temperature solution and as-grown crystals have been characterized. Large size lead-based scintillators, $PbWO_4\;and\;PbF_2$ crystals, have been mass-produced by the vertical Bridgman method in the multi-crucible fumace. These crystals have been supplied to CERN and other laboratories for high-energy physics experiments. The Bridgman growth of piezoelectric crystals $Pb_5Ge_3O_{11}\;and\;Pb_2KNb_5O_{15}$ are discussed also.

Enhancement of electromechanical properties in lead-free (1-x)K0.5Na0.5O3-xBaZrO3 piezoceramics

  • Duong, Trang An;Nguyen, Hoang Thien Khoi;Lee, Sang-Sub;Ahn, Chang Won;Kim, Byeong Woo;Lee, Jae‒Shin;Han, Hyoung‒Su
    • 센서학회지
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    • 제30권6호
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    • pp.408-414
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    • 2021
  • This study analyzes the phase transition behavior and electrical properties of lead-free (1-x)K0.5Na0.5NbO3-xBaZrO3 (KNN-100xBZ) piezoelectric ceramics. The stabilized crystal structures in BaZrO3-modified KNN ceramics is clarified to be pseudocubic. The polymorphic phase transition from the orthorhombic to pseudocubic phases can be observed with KNN-6BZ ceramics considering the optimized piezoelectric constant (d33). Electromechanical strain behaviors are discussed. Accordingly, the enhancement of strain value at x = 0.08 (composition) may originate from the coexistence of ferroelectric domains and polar nanoregions. A schematic of domains for KNN, KNN-8BZ, and KNN-15BZ ceramics has been proposed to describe the relationship between the stabilized relaxor and changes in electrical properties.

$Pb(Fe _{1/2}Ta_{1/2})O_3$의 합성, 유전특성 및 질서배열구조 (Syntheses, Dielectric Properties and Ordering Structures of $Pb(Fe _{1/2}Ta_{1/2})O_3$)

  • 우병철;김병국;김병호
    • 한국결정학회지
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    • 제13권3_4호
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    • pp.165-171
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    • 2002
  • 고상반응법에 의해 합성된 분말을 $1100^{\circ}C$에서 소결함으로써 밀도가 $9.3g/cm^3$이고 평균입경이 $5.1{\pm}1.2{\mu}$$Pb(Fe_{1/2}Ta_{1/2})O_3$를 단일상으로 합성하였다. (공간군: Pm3m) $-150{\sim}50^{\circ}C$에서 측정된 비유전율은 인가전압의 주파수가 1kHz일 때 $-41^{\circ}C$에서 비유전율이 3100으로 최대값을 가지고 유전완화(dielectric relaxation)현상 및 완만한 상전이(diffuse phase transition, DPT)가 뚜렷하게 관찰되는 전형적인 완화형 강유전특성을 보였으며 소결후 $1000^{\circ}C$에서의 열처리 시간이 증가함 에 따라 상전이의 완만화도는 감소하여 정상 강유전체화 하였다. 한편, 소결직후 $Fe^{3+}$$Ta^{5+}$ 이온은 투과전자현미경으로도 검출할 수 없는 정도의 단거리 영역에서 화학양론적으로 1 : 1 질서 배열하고 있으며 이러한 B자리 양이온의 질서배열은 열처리 시간이 증가함에 따라 강화됨을 라만분광법으로 확인하였다. 소결직후 $Pb(Fe^{12}Ta_{1/2})O_3$센서의 완화형 강유전특성은 B자리 양이온의 화학양론적 1:1 단거리 질서배열구조와, 열처리한 $Pb(Fe_{1/2}TA_{1/2})O_3$에서의 완화형 강유전특성 감소는 열처리에 따라 강화된 화학양론적 1:1 단거리 질서배열구조와 연관지을 수 있었다.

Bi0.5(Na0.78K0.22)0.5TiO3 세라믹스의 A-site 비화학양론이 유전 및 전기적 특성에 미치는 영향 (A-site Non-stoichiometric Effects of Bi0.5(Na0.78K0.22)0.5TiO3 Ceramics on the Dielectric and Electrical Properties)

  • 박정수;이규탁;윤지선;조정호;정영훈;백종후
    • 한국전기전자재료학회논문지
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    • 제27권12호
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    • pp.803-808
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    • 2014
  • $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

Effect of Electric Field Concentration by Electrode Patterning on the Incipient Piezoelectric Strain Properties of Lead-Free Piezoceramics

  • Kang, Woo-Seok;Hong, Chang-Hyo;Lee, Young-Jin;Choi, Gangho;Shin, Dong-Jin;Lim, Dong-Hwan;Jeong, Soon-Jong;Jo, Wook
    • 한국세라믹학회지
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    • 제56권6호
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    • pp.549-557
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    • 2019
  • More than two decades of world-wide research efforts have resulted in several classes of potentially important materials. Among them are incipient piezoelectrics, which are especially useful for actuator applications. However, relatively large electric fields are required for activating the large incipient electromechanical strains. So far, many attempts have been made to reduce the required electric field by intentionally inhomogenizing the electric field distribution in the microstructure through core-shell and composite approaches. Here, we show that electric field concentration can be realized simply by adjusting electrode patterns. We have investigated the effect of electrode patterning on the incipient electromechanical strain properties of an exemplarily chosen lead-free relaxor system, revealing that electrode patterning does have a significant role on the strain properties of the given lead-free relaxor system. We believe that this approach would make a new strategy for ones to consider bringing the functional properties of electroceramics beyond their conventional limit.

(Ba,Ca)SiO3 Glass Frit 첨가에 따른 NKN-BT 세라믹스의 유전 완화 특성 (Dielectric Relaxation Properties of KNN-BT Ceramics with (Ba,Ca)SiO3 Glass Frit)

  • 배선기;신혜경;이승환;임인호
    • 한국전기전자재료학회논문지
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    • 제27권6호
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    • pp.367-371
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    • 2014
  • We investigated dielectric relaxation properties of $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ ceramics by addition (0~0.3 wt%) of $(Ba,Ca)SiO_3$ glass frit. All composition of $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ added $(Ba,Ca)SiO_3$ glass frit showed the same crystallographic properties, coexistence of orthorhombic and tetragonal phase. By increasing addition of $(Ba,Ca)SiO_3$ glass frit, the Curie temperatures of $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ ceramics were decreased, whereas maximum dielectric constants of $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ ceramics were dramatically increased. Especially the deviations of Curie temperature $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ ceramics were increased by increasing amount of $(Ba,Ca)SiO_3$ glass frit, and it indicated that $0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$ ceramics added $(Ba,Ca)SiO_3$ glass frit have relaxor characteristics.

TSDC 방법을 이용한 AC 폴링된 PMN-PT 단결정의 디폴링 메커니즘 분석 (Depolarization Mechanism of Alternating-current-poled Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals Measured using in-situ thermally Stimulated Depolarization Current)

  • 이건주;김황필;이상구;이호용;조욱
    • 센서학회지
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    • 제29권1호
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    • pp.59-62
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    • 2020
  • Currently, increasing attention is being paid to relaxor-based ferroelectric single crystals in photoacoustic images, especially for high-end applications. Among the crystals are (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-100xPT) single crystals located near their morphotropic phase boundary (x = 0.30-0.35) because of their ultrahigh piezoelectric and electromechanical coupling properties. The alternating current poling (ACP) treatment, rather than the conventional direct current poling treatment, has recently been spotlighted due to its effectiveness in enhancing the piezoelectric properties. So far, it has been suggested that the enhanced piezoelectricity originates from either a domain miniaturization to nanodomains or from an electric-field-induced monoclinic symmetry. In this study, we demonstrate by thermally stimulated depolarization current measurements that the effect of ACP is too complex to be explained using a single mechanism and that the proposed electric-field-induced monoclinic symmetry is unlikely to exist.